1. Field of the Invention
The present invention relates to an information reproducing apparatus which decompresses compressed information that is recorded on a disc and outputs the decompressed information as reproduction information.
2. Description of the Related Background Art
A mini-disc player, which is one type of information reproducing apparatus, has a DRAM (Dynamic Random Access Memory) for temporarily storing compressed data. In utilization of the DRAM, it is possible to improve vibration resistance by increasing the amount of information stored in the DRAM. The DRAM temporarily stores compressed information which has been read from an mini-disc by a pickup, while the compressed information that has been stored is read and then is expanded by a decoder, before being output as reproduction information. It is possible to reproduce by decompressing the compressed information in the DRAM while data including a misread error is read again, even when a read error is caused by vibration. Therefore, a problem of intermittent sound, so called skipping, can be prevented.
In playback of the mini-disc, when compressed information is stored in the DRAM up to the allowable storage capacity thereof, reading operation of the pickup is stopped. When the amount of compressed information stored in the DRAM decreases to permit storage of additional information, the pickup resumes the reading operation thereby storing the compressed information that has been read into the DRAM.
In the conventional mini-disc player, operation of a servo system including a spindle servo, which is related to reading data from a mini-disc, is not necessary during a writing-interruption period until the amount of compressed information stored in a memory such a DRAM decreases to a storage amount which permits restarting writing after reaching the allowable storage capacity in the memory. It is preferable to reduce power consumption by stopping, for example, a spindle motor, during the writing-interruption period. However, if the power supply to the servo system is completely stopped during the writing-interruption period, after the amount of data storage in the memory has decreased to the storage amount which permits restarting writing, a restart of data reading from the mini-disc by the pickup is delayed.
This problem is not limited to a mini-disc player. It also occurs in other information reproducing apparatuses each of which, for reproduction of compressed information recorded on a disc, write the compressed information to a memory and then read the compressed information from the memory for expansion and output the expanded information as reproduction information.
An object of the present invention is to provide an information reproducing apparatus which reduces power consumption during a writing-interruption period, and restarts writing to a memory immediately after termination of a writing-interruption period.
According to the present invention, there is provided an apparatus for reproducing information by expanding compressed information recorded on a disc, comprising: spindle driving means for driving a spindle motor for rotating the disc; reading means for reading the compressed information from the disc rotated by the spindle motor; memory control means for writing the compressed information read by the reading means to a memory, to read out the compressed information written from the memory in the order of writing and for supplying the read information to expansion means for expanding the compressed information read by the memory control means and outputting reproduced information based on the expanded information; and storage amount control means for stopping the writing of the compressed information to the memory by the memory control means when an amount of the compressed information unread from the memory after writing thereto increases to a first predetermined amount and for restarting the writing of the compressed information to the memory by the memory control means when the amount of the compressed information unread from the memory after writing thereto decreases to a second predetermined amount which is smaller than the first predetermined amount and which is an amount corresponding to the compression ratio of the compressed information, wherein the spindle driving means decreases the rotational speed of the spindle motor during a writing interruption period for a time from stoppage of the writing of the compressed information to the memory by the storage amount control means to the restarting of the writing, to a lower speed level than a rotational speed level of the spindle motor during a writing period when the compressed information is written to the memory.